This study will assess the influence of the persistent opposition to experimentation involving living animals, especially mammals, on the conduct of biomedical research in America in the twentieth century. After World War I, America emerged as the world leader in medical research, yet even in the so-called 'Golden Age of American Medicine" medical researchers continued to experience difficulties in obtaining sufficient animals for use in laboratories at a direct result of antivivisectionist activities. Accusations of laboratory animal abuse and political battles over the research use of pet dogs and cats obtained from municipal pounds had far=reaching consequences not only for the biomedical research process but for biomedical research journalism as well. This project, which relies on the methods of social and intellectual history to evaluate archival materials and published documents, will examine the American antivivisection movement and its impact on biomedical research in the twentieth century by addressing several interrelated themes: the sources of laboratory animals and the ways in which these arrangements were interrupted by antivivisectionists; the growing importance of pets in American society and the effect on the controversy over pound animals; the role of the media on both sides of the antivivisection issue, for example, the public education campaigns conducted by such research advocacy groups as the National Society for Medical Research (established 1946); the influence of antivivisectionist criticism on the publication of experiments involving animals; and the impact of federal regulation of the use of animals in the laboratory beginning with the first federal legislation, the Laboratory Animal Welfare Act (1966).